One of the individuals helped me until I was able to open it
OP, I have followed your post from the beginning and I must say, you did not give sufficient details that will enable people here help you. Yet, everyone has tried to help you. You said one of the individuals helped you until you were able open it, open what exactly?
Are you saying you've been able to recover your wallet? If that's the case, then that's great.
Can I know the purchase date in the application that I added it to
If what you mean by purchase date is knowing when you performed the transaction, this link below will enable you see the transaction analysis in that wallet from the day it was created.
https://blockexplorer.one/Unless application you used offer both wallet and exchange feature, the answer is no.
Were applications that offer both wallet and exchange features available as at 2020/2021? I am new in this industry, I can only know what happened even last year by reading. I read somewhere that wallet and exchange feature in one application only started recently, is he wrong?
You need to remember which wallet application and exchange you used few years ago. Have you tried checking your old email or browsing history?
This is a very good recommendation, only if OP has the patience to go through this their email.There are chances that he will find solution there.
I don't want to be too pessimistic, but this looks like one of those simple scam schemes where someone "sells" someone Bitcoin, but actually sells them a public address in a watch-only wallet. In any case, the OP should have something more than that, otherwise he can look at that address for the rest of his life.
I became aware of the watch only wallets few days ago when someone approached me with a Trustwallet app with much balance inside. He was struggling to withdraw the coins, that it's his profits from trading. When I saw watch only wallets, I knew what it means as the name implied. You can only watch but cannot transact. I was able to tell him that, he's not incharge of those coins, that he can only view the balance. Although, he wasn't satisfied. I didn't bother much because I knew he can't make such amount of profits from trading. From your post, it's obvious my friend was scammed. I will check on him tomorrow.