Hello,
Pursuing a 3 year LLB at GLC parallely a 21 month CS articleship is permitted but quite challenging. Because it requires tight schedules and attendence. For attendace structure, GLC requires a minimum of 75% attendance. If you feel okay with this you can try to take decision. Decide based on your mindset and lifestyle.
I have attached a link for GLC Mumbai admission and other details, You can refer with that link too.
https://www.careers360.com/colleges/government-law-college-mumbai
I hope this helps you.