comma + conjunction

[allfta]

I always appreciate many guyz here in this site.
Here's my question.
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1.
As Stacey said in this post (https://www.beatthegmat.com/health-care- ... 60-15.html), two below sentences are all correct.

She doesn't like playing sports but does like watching them on TV.
She doesn't like playing sports, but she does like watching them on TV.

I wonder another form of "She doesn't like playing sports, but does like watching them on TV. " can also be treated as a flawless answer in GMAT. In my understanding, we don't need comma in front of conjuction but.
But, check this thread (https://www.beatthegmat.com/health-care- ... 40660.html).

The OA is D and it includes comma + conjunction form even the following clause shares same subject with the first one.
So, my quetion is, can i use comma in the two given situation wihtout any restrictions?


2. I am clear that possesive adj. + gerund form is not preferred in GMAT. Then, how about three below forms?
1) possesive adj. + present participle
2) possesive adj. + past participle
3) any adj. + gerund

[Jim@Grockit]

1. A comma will always be correct, though it's possible to have too many commas in a sentence due to other modifying phrases. The comma can be left out when there is not a new subject, although many writers will still include it.

2. Do you mean possessive pronouns (his, her) rather than possessive adjectives? If you do, you would never see a possessive pronoun modifying a participle of any kind, because participles are verbal adjectives, and you cannot modify adjectives with other adjectives.

[allfta]

1. A comma will always be correct, though it's possible to have too many commas in a sentence due to other modifying phrases. The comma can be left out when there is not a new subject, although many writers will still include it.

2. Do you mean possessive pronouns (his, her) rather than possessive adjectives? If you do, you would never see a possessive pronoun modifying a participle of any kind, because participles are verbal adjectives, and you cannot modify adjectives with other adjectives.

@ Jim@Grockit
Thank you!!
In question 2, yes I mean possessive pronouns. Your explanation is clear but I would like to confirm that possessive pronouns + gerund is not preferred in GMAT. Is it right? I am not sure that adj.(possessive pronouns) can't modify noun (gerund). Q1)

And I met a guy who told me, I can't use something like "analysts' predicting" form. the word analysts' is not a pronoun. What do you think of this case? Q2)

Plus, then is it wrong to use any adj. as a modifer of participle? For example, beutiful singing birds. Q3)