what is the max i2c devices i can connect?
it is a bus; you can connect as many as you need. You will however find that you need unique addresses to have them work correctly, so theoretically that limits you to 128 uniquely identified devices. Also remember that some “devices” are actually composite devices that have morethan one 7-bit I2C address, so that decreases the number.
This question has too many factors and there is no answer for it.
Let me ask you this, how many do you need to connect?
like 5 or 6 devices
Yes you can
now uart cannot be shared, right?