I understand #1 below can be simplified into #2, and #3. How about #4 and #5? Are they grammatically correct and do they make sense?

1. He plays tennis as well as his father plays tennis.

2. He plays tennis as well as his father does.
3. He plays tennis as well as his father.

4. He plays tennis as well as his father plays it.
5. He plays tennis as well as his father plays.


8769

 

"Are they grammatically correct and do they make sense?"

Yes, and yes. Are they simplified forms? No.
Are they idiomatic? #4 is, in some contexts. #5 sounds like something from a not very good childrens' book.

 

Well, they're grammatically correct, but some of them sound a bit odd. The only sentence from that list I would use is #3.

 

I vote for #3.
There is no repetition or redundancy and the meaning can not be unintentionally misconstrued.

.,,

 

Actually, I think #3 could be misconstrued, depending on how it was phrased when spoken or read when written.

"He plays tennis as well as his father" could mean "both he and his father play tennis."

I vote for #4. "He plays tennis as well as his father does."