തള്ളൽ

No, it's not a swear word. It's just very informal slang. It's like saying 'You're capping' in English.

Yes, 'Thallal' is the literal word for 'a push'. Context tells the listener if you mean a physical push or a lie.

A female boaster is called a 'Thallukari' (തള്ളുകാരി).

You can say 'Thallൽ nirthee' (തള്ളൽ നിർത്ത്) or 'Thallalle' (തള്ളല്ലേ).

Yes, it is universally understood across Kerala, though the accent might vary.

Only if the atmosphere is very casual and you are joking with colleagues. Otherwise, avoid it.

There isn't a direct slang opposite, but 'Yadharthyam' (Reality) or 'Sathyam' (Truth) are the formal opposites.

In Kerala, 'Trolls' are satirical memes. Calling out 'Thallal' is the most common theme of these memes.

Yes, 'Thallalukal' (തള്ളലുകൾ), but it's rarely used. People usually just say 'Kure thallu' (Lots of thallu).

In slang, yes. 'Thallu' is the shorter, punchier version.

Yes, in some contexts 'Thallu' can mean a physical fight or brawl.

The literal word is ancient, but the slang meaning became popular in the last 15-20 years.

It's a retroflex 'L'. Curl your tongue back. If you use a normal 'L', people will still understand, but it won't sound native.

Literally a push-cart, but slang for a person who never stops boasting.