Can I own more than one private and public key?

[Asiska02]

1. Can I own more than one private and public key? For instance, I want to send my public key to more than one person to receive bitcoin. Can I send same public key to them to receive the bitcoin and unlock with the same private key? Or a new one needs to be generated when sending to more than one person?

2. What does the public key starts with the number “04”?

[OmegaStarScream]

1. Each address is associated with a private key, that private key is required to spend your funds. You can use the same address multiple times, but that's not recommended (for privacy reasons).

2. If you're referring to public addresses as I believe you are, then these can only start with 1, 3, or bc1.

[PawGo]

1. Can I own more than one private and public key? For instance, I want to send my public key to more than one person to receive bitcoin. Can I send same public key to them to receive the bitcoin and unlock with the same private key? Or a new one needs to be generated when sending to more than one person?

You may have as many keys/addresses as you want. You may also use one address for everything - as long as it is not a problem for you that different senders will see your other transactions. A "good habit" is to use different addresses for different purposes or even generate a new address for each incoming transaction.
But from technical point of view, there is no limitation.
BTW, you want to send "public address" maybe, not "public key", right?

2. What does the public key starts with the number “04”?

Public key starting with "04" has "uncompressed" format, which means it contains both X and Y parameter of the point it represents - key is "long".
Otherwise, you may have key which starts with "02" or "03", and then it contains only X param of the point. Y could be deducted, depending if it should be "positive" or "negative" (higher or lower on the curve).
You may compare it for example here: https://learnmeabitcoin.com/technical/public-key
Since around 2013 uncompressed keys are almost not used.

[hosseinimr93]

It seems that you are confusing public key with address. However your bitcoin address can be derived from your public key, it's not common to give your public key to people. You should give your address to others.

Anyways, as mentioned above by OmegaStarScream and PawGo, any address can be used for receiving bitcoin numerous times. So, you can give a single address to as many people as you want. All of them will be able to send bitcoin to you.

However it's possible to reuse an address, due to privacy reasons, that's not recommended to do so.  
Note that all bitcoin transactions are public and anyone who knows your bitcoin address can easily check your previous transactions and know how much bitcoin you have.

If you want to protect your privacy, I recommend you to use a HD wallet instead of using a single address and a single private key.
In a HD wallet, you have numerous addresses derived from a seed and you can use a new address whenever someone is supposed to send bitcoin to you.

[Asiska02]

1. Can I own more than one private and public key? For instance, I want to send my public key to more than one person to receive bitcoin. Can I send same public key to them to receive the bitcoin and unlock with the same private key? Or a new one needs to be generated when sending to more than one person?

You may have as many keys/addresses as you want. You may also use one address for everything - as long as it is not a problem for you that different senders will see your other transactions. A "good habit" is to use different addresses for different purposes or even generate a new address for each incoming transaction.
But from technical point of view, there is no limitation.
BTW, you want to send "public address" maybe, not "public key", right?

2. What does the public key starts with the number “04”?

Public key starting with "04" has "uncompressed" format, which means it contains both X and Y parameter of the point it represents - key is "long".
Otherwise, you may have key which starts with "02" or "03", and then it contains only X param of the point. Y could be deducted, depending if it should be "positive" or "negative" (higher or lower on the curve).
You may compare it for example here: https://learnmeabitcoin.com/technical/public-key
Since around 2013 uncompressed keys are almost not used.

1. Can I own more than one private and public key? For instance, I want to send my public key to more than one person to receive bitcoin. Can I send same public key to them to receive the bitcoin and unlock with the same private key? Or a new one needs to be generated when sending to more than one person?

BTW, you want to send "public address" maybe, not "public key", right?

What is the difference between the “public address” and “public key”? Aren’t they the same thing?

1. Each address is associated with a private key, that private key is required to spend your funds. You can use the same address multiple times, but that's not recommended (for privacy reasons).

Does that mean using the same address without changing it does not guarantee its safety? Even if my private key is safe with me always?

[PawGo]

1. Each address is associated with a private key, that private key is required to spend your funds. You can use the same address multiple times, but that's not recommended (for privacy reasons).

Does that mean using the same address without changing it does not guarantee its safety? Even if my private key is safe with me always?

It has nothing to do with your private key, but with your privacy.
You may use one address for the whole life, but it will be easy (ok, not very easy, but easier) to trace your transactions, your actions, where you pay, who pays you etc.

[OmegaStarScream]

Does that mean using the same address without changing it does not guarantee its safety? Even if my private key is safe with me always?

Your funds will remain safe, but as I said, this is for your privacy. If you keep using the same address everywhere, people will be able to link YOU with that address.

And as mentioned above by hosseinimr93, most wallets nowadays generate a new address for you each time you receive funds, so it's not like you have to keep track of all these addresses/PKs manually.

[Asiska02]

It seems that you are confusing public key with address. However your bitcoin address can be derived from your public key, it's not common to give your public key to people. You should give your address to others.

Anyways, as mentioned above by OmegaStarScream and PawGo, any address can be used for receiving bitcoin numerous times. So, you can give a single address to as many people as you want. All of them will be able to send bitcoin to you.

However it's possible to re-use an address, due to privacy reasons, that's not recommended to do so.  
Note that all bitcoin transactions are public and anyone who knows your bitcoin address can easily check your previous transactions and know how much bitcoin you have.

If you want to protect your privacy, I recommend you to use a HD wallet instead of using a single address and a single private key.
In a HD wallet, you have numerous addresses derived from a seed and you can use a new address whenever someone is supposed to send bitcoin to you.

I was able to understand and picture it well on how it works now. Thanks for the explanation, I now get everything now.