Answer 1

At least 3, all of which you have tagged.

Answer 2

For front-end development you need to learn html,css, javascript, PHP,Node js ,Sql.

You can search on Google which languages using in front-end development.
This is repeted question
You can read these old post you can find better answer
https://www.sololearn.com/discuss/1104527/?ref=app
https://www.sololearn.com/discuss/841331/?ref=app
https://www.sololearn.com/discuss/1315142/?ref=app
https://www.sololearn.com/discuss/1107237/?ref=app
https://www.sololearn.com/discuss/1707820/?ref=app
https://www.sololearn.com/discuss/1424002/?ref=app
https://www.sololearn.com/discuss/1963651/?ref=app