Iphone 7 plus home button replaceable or not??And if replaceable how much it cost??

See also this:

Genius Bar Reservation and Apple Support Options - Apple

Apple will most likely offer you an out-of-warranty replacement unit. Please note that, should you try to have this repair done by anyone other than Apple or an Authorized Apple Service Provider, you will probably not be able to use TouchID ever again.

Hello,

Hmm, difficult to answer. Start here: iPhone Repair

It should be checked. They will explain your repair options: Find Locations

Good luck.