I hope you resolved your issue by now. For the purpose of others who may have the same issue here are the answers:
1)Does Canadian gov accepts [Refugee's] Travel document?
2) if yes, do I need to apply for visit /tourist visa or ETA.
3) Online or paper application?
Paper application seems to be the safest bet
4) How much time does the visa process takes?
Depends on where you are applying. You may check this link
from the Canadian government.
C$ 100 (as of now)
Hope this will help someone with similar issue.