Pls once tell with an example...

Yes Every Subgroup of an Abelian group is Abelian ,because in Abelian group every element posses Abelian nature i.e., commutativeness soo all subgroups can be Abelian

Every Subgroup of an Abelian group is Abelian , but every Subgroup of a group is may / may not be Abelian. And A non abelian group can have an Abelian subgroup

Abelian group will always have abelian subgroup . Every subgroup will not be abelian in general. Take Q8 which is not abelian but has a cyclic subgroup of order 4 generated by .

Refer attached explanation