Word that describes someone belittling themselves or their actions while actually thinking the opposite

Question

I'm looking for a word or a phrase that would best describe someone who criticises parts of themselves or actions they have taken while secretly thinking the opposite, be it to boost their ego by seeking pity or to make their achievements greater when they inevitably turn out to be a success.

Answer 1

false modesty (n.)

Behavior in which a person pretends to have a low opinion of his or her own abilities or achievements Cambridge

Affected or pretended modesty concealing pride. Lexico

Answer 2

The person is humblebragging.

Quoting from grammarly.com:

Your friend complains about how swamped she is in her new director role. She’s so stressed, in fact, that she’s lost 10 pounds and can even fit into her old jeans from high school. 
As the listener, you translate your friend’s series of “complaints” and deduce the real meaning behind the brag—she’s proud of her new position and knows she looks better than ever.
This is the art of the humblebrag.

and from Cambridge dictionary:

humblebrag.
noun [ C ]   humorous.
UK /ˈhʌm.bəl.bræɡ/ US /ˈhʌm.bəl.bræɡ/.

something you say which appears as if you are complaining or embarrassed, but is really a way of telling people about something that you are very proud of:
She posted a classic humblebrag about spending $2,000 on a handbag "because I'm so terrible with money".