I don't think nodes check or update the UTXO set for transactions in their mempool which means the transaction with a duplicate txid should not be rejected from the mempool. They update the UTXO set after they receive the mined block and after verification by which time the tx and the block containing it would be rejected.

3 easy ways that anyone without any technical knowledge could use to quickly tell if a project is closed source are:

1. Having an actual source code
If a project claims to be open source it has to have a source hosted somewhere. That means you have to be able to see actual code. Usually there is either no source code to be found or something else the scammers do is to share binaries (eg .exe) on Github pretending to be open source.

2. How active the repository is
You can reject a lot of fake claims using this. For example a project claims to be open source and has real source code on Github too. This project released a new version (eg. on google playstore) today but the code on Github was updated a year ago. That is a clear indication that the project is not open source.

3. Dependencies
Although this is a bit technical I don't think it is that hard. Sometimes what scammers do to pretend their project is open source is to release part of the code (usually UI related code) and use a closed source backend that does everything else.
Usually the name of the repository, the explanations in the readme file or the dependencies in the dependency section of the project show you what part of the code you are looking at.

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These are easy ways to figure out "closed" source software, but in order to be able to tell if a project that doesn't fit into the 3 above categories is open source (eg. Electrum) you have to be able to review the whole code which requires programming knowledge and time.
You'd have to also look into the external libraries the project is using and whether those libraries are open source and if the project is using the same binaries (built from that code not something else with the name).

It's a bit of a late response but I hope this answers your question since I didn't see anybody cover these.

Think of fiat as a unit of measurement, it is not perfect since it is inflationary but it is a lot better than using anything else.
When we report the price of anything in fiat, the point is to quickly understand how much something is worth. For example if I say something is worth 20 dollars, euros, yuans, rubles, rials,... everyone reading this would quickly understand what value I'm talking about but if I said something is worth 20 ounce of gold, most people won't know how much that is worth and have to do some conversion to really understand it.

Besides gold's value and price are both changing. It is not as fixed as you'd think.

That is not collision, that was creating the same exact coinbase transaction ergo having the same exact hash. That was easy to happen too in the past since block fees weren't full in 2012 and fees were sometimes zero so the amount field of the output were the same, if the miner were the same too and reused address the whole tx would have been the same.

BIP34 mandated blocks to include the height (which is different for each block) in the coinbase script which means even if the coinbase of 2 blocks are exactly the same in everything else, they will be different in at least one place ergo have guaranteed different hashes.

When we say "altcoins" we are talking about a massive world that consists of a lot of different projects (a couple of categories). So we have to be clear which category we are talking about.

The main category of altcoins are those that are usually referred to as "shitcoins". These are useless coins usually with severe flaws and exploits that are also usually centralized. In one word we can call them "useless".
These coins will continue to exist under all circumstances because the purpose they serve is for gamblers to make bets on their prices and participate in their pump and dumps to make a quick profit.
All tokens and token creation platforms are part of this category.

Another category of altcoins are those that tried a different approach, like using a different mining algorithm (eg. LTC). These coins had nice ideas but none of them could solve any real problem which means they can be considered "failed projects".
They will lose popularity over time and eventually die in the future. Again this is regardless of what happens to bitcoin.

A final category could be same as the one before but coins that had some innovation and could solve some actual problem hence gain some utility (eg. XMR). These coins will remain relevant and could even grow over time. But their future heavily depends on their competition, meaning if another project comes along with better innovation that solves the issues they had (eg. scaling problems of XMR) they would easily and quickly replace the said coins.
Bitcoin's mass adoption could make things harder for these coins.

High inflation has a positive effect on bitcoin price as it pushes people into investing their money and one of their investment targets is always bitcoin.
What affects bitcoin negatively is recession which is what pushes people into liquidating their assets so that they can "live"!

What we had over the past year (and still do) is a combination of inflation and recession which is what led to the initial crash. We still have high inflation and recession in a lot of the world including US, but what you are forgetting is that more increase in interest rates by the FED is not going to have any effects on reducing the inflation or causing any more recession than this.
In other words there is no reason to expect any kind of drop because of the ongoing recession in US specially since almost all of those who wanted to sell have already sold their bitcoins.

The only way we could see a big drop in bitcoin price is either a massive market manipulation or a massively negative and sudden economical event. Anything that is ongoing is not going to come at a shock and cause a drop like dollar value dumping, inflation remaining high, US banks shutting down, and so on.

CIA released a bunch of fake documents after the leak to try and create such doubts about the authenticity of those documents and also to spread their propaganda. In other words they did it to make the best out of a bad situation.

That just proves that you have no idea what is going on in the world.

The hardware doesn't change that much and when it  does, it is backward compatible meaning a code that ran well on a hardware that existed in 2008 will run successfully on a hardware that exists in 2023. In fact there are very specific and rare cases where you'd have to test the code on different hardware to make sure it runs correctly, cases like handling endianness, using CPU intrinsic, etc. which again rarely need intervention. In fact if you check the bitcoin core code involving these things (eg. implementation of SHA256) you can see that the code doesn't really change with each release.

There are about 200 countries in the world and no 2 governments see eye to eye on any subject. It is not possible for all of them to suddenly decide to take down all exchanges globally! Not to mention that each time a government does this, it is an excellent business opportunity for everyone else because all the money from that country that went into those exchanges would go abroad.

Additionally you don't have to use an exchange to acquire bitcoin. Bitcoin is a currency and like any other currency you can and should earn it.

Good for those who did then

That is not even comparable. Ukraine is under occupation for the second year while Palestine is under occupation for the 75th. The genocide in Palestine over this period is also not even close to any other genocide in human history.

When Ukraine map and its occupied regions started to look like this you can start comparing the two:

It depends on how you store it and how you use it.

For example it could be stored as binary (instead of hex in a text file) and in its compressed form. That is 33 byte per pubkey and a billion of them makes it a 33 GB file (65 GB for uncompressed).

As for usage of this data, you don't need to load it all in memory. You could use a database and/or sort the list in a way that would make it faster to search using methods such as binary search, etc.

Rumors are not always rumors, they are sometimes social experiments to see what people think. If they react positively to such a silly plan they could move ahead with it otherwise they could think twice, for example.

In this case I'd say this is absurd because there is no reason for a "social media" platform to become also a trading platform. Not to mention that the Twitter owner Musk, is known for his attempts at market manipulation and this may be another desperate attempt at gaining an influence on the altcoin market again.

The value remains the same, the price would go up and I'd argue that altcoins' price is not going to go up because of inflation since they work based on pump and dumps and most of them are only traded against bitcoin not even against fiat to be affected by fiat value.

No it is not a guarantee. The main reason for big rises will always be more adoption.
Inflation will both directly and indirectly affect the price. Directly in the sense mentioned above (devaluation of fiat) and indirectly by pushing more people toward making an investment in bitcoin that doesn't suffer from the same flaws as fiat does.

No! Non-stop money printing ruins the economy of the country. Look at US.

It is more like bcash holders who know they are bag holding garbage and want to switch to something else while everyone tells them not to because everything is fine with bcash.

You can't correct a correction!
Going back up to $30k is only part of the correction to get bitcoin price back to a more realistic level that is closer to its intrinsic value. There is no logical reason to see it drop back down again. The only way we can see another drop is market manipulation and another wave of panic sells or when the economy crashes harder (at a different pace otherwise it is already crashing).

The recent leaked classified documents out of United States shows that US intelligence does not see any hope for Ukraine in this fight and they also don't see any end to it (or any progress) this year either. This means the West is going to continue pouring money into this war continuing the same path as last year with higher inflation and recession and deindustrialization of Europe.

As for the world Economy, any country that succeeded over the past year to not get sucked into this conflict or obey the US demands (like replacing cheap Russian energy with very expensive US energy) is going to continue strengthening their economy and expand their GDP. Possibly a lot more in 2023 compared to 2022 and even more in 2024.
This process will become faster as dedollarisation continues since countries that dump the Dollar will be less affected by its inflation and more importantly they are eliminating United States ability to put any kind of pressure on them to enforce its demands.

As far as statistics go, theirs is a decent work. But some of the nodes they list specifically in the first page are spy nodes not real full nodes that are maliciously and intentionally placed there.

Considering that the charts showing number of nodes is updated on daily basis, I would assume the links you shared are also up to date.
https://luke.dashjr.org/programs/bitcoin/files/charts/historical-dygraph.html

Oh. I always automatically assume that the coins someone has is received from a third party (no access to that address).

Yeah, They receive the same level of help regardless of the "offer".

Something that people using this argument involving halving forget is that each halving the reward reduction is smaller than the previous one. The first halving the block reward dropped by 25 bitcoins whereas the upcoming halving the reward will only drop by 3.125 and when the reward reduced by 25 bitcoins, the hashrate only grew, there is no reason to argue that when the reward reduces less the hashrate would drop.

In a couple of more halvings the before and after reward won't be that different.

If OP could sign message from that address he wouldn't have been here since signing a message requires having the private key
Although if you want to not-doubt his story OP could share the public key + address. Considering that hashes inside addresses are not reversible to get the public key, the chances of it being a fake story diminishes significantly.
Although if you want the "reward" none of the above would help, you'd need to use an escrow