This looks like kedai bawah pokok alignment.

properly aligned car should not wear like this.

Next time do it outside, alignment every 10k km, dun let your SC do dy.

There are good SCs, yours is just very bad at doing alignment.
1) Should I replace both the front tyre? Or only the worn out one?
BOTH.

2) What are the recommended brands / models? So far I heard Michelin XM2 is good for Myvi.
Eco Tyres are more or less the same. Go for reputable brands, and anything EXCEPT Ling Long, silverstone, viking and dunlop.

3) If I do get 2 new tyres, should I put it as the back tyre, and use the back tyre (old ones) as front tyres?
YES.

4) Any recommendation on good tyre shops around PJ, KL? Best bang for buck type. lol.
Pusat Servis Tayar Weng Heng at jalan kemuning,
or Hin Leong Tyre Services at klang