questions

I am wondering on a few things.


First of all, how do you put a password on your router? Like, when you type your default gateway in on the web address, and it asks for the user and password to access your router, the default is user: admin password: password or something like that. It varies for different routers too.
But I would like to know how to change THAT password. How do you do so?

Second question: This is sort of a weird/crazy question, but... Say someone was abusing your router and typing in random password and usernames to try to access your router, if they didn't know the password at all, and they kept abusing it, would that slow/DOS/DDOS your router/Internet at all?

Third question: Is it possible on your router to limit devices/computers connected? So say, you only wanted 2 devices/computers connected, when a third device/computer tries to connect to your router/network, they wouldn't be able to at all. Is this possible?

And last but not least question, is it possible to put a VPN on your router? So, for example, say some random person just connected to your network/router from next door, and they had no Idea what a VPN was, they just had a brand new computer with nothing on it. When they go on your network/router, and type in on google "What is my ip" the VPN IP would come up. Is this possible? If so, is it also possible to make your router secure where no one can retrieve the actual IP Address to the ISP but the person who knows the router's password?
Update: Sorry, I ran out of room, and everything I said, what router will fit the criteria perfectly? Can you give me a good one that's cheap/fast/secure? Thank you all so much :')
Update 2: And also, what fast/secure cheap major VPN Service works on routers?