No, u have to visit JPJ to apply & get the L license.

Now not really clear on the procedure as before this you sit for undang again tk get the L, but now they made it so that you don't need to sit for undang the 2nd time if you already have an existing license, theoretically you can get the L without doing much. Best you just call up a driving school near you.

B full L license if not mistaken need to renew every 6 months for up to 2 years.

Just go to Jpj counter ask for b2 to b full upgrade, the counter officer will request u to fill a form, get a photo & $$$ for L license.
Later go to driving  school to apply b full driving package (kpp03, QTI & Jon test). It cost about 500rm in my place.
For L license, max period is 2yrs.

I took my b2 last year still need to go for undang test.

Yes you have to go to jpj to do it.
Prepare 1 passport photo white background, 1 copy of ic and fill up the form.
Then they will ask how long you want the L license to be, 3 or 6 months, if 6 pay RM40