Hello Aspirant,

B.Tech is a 4 year course and doing a diploma in engineering can take you into B.Tech program through lateral entry, but the specialization matters here .Civil to CSE is not possible so no, you cannot join B.Tech through lateral entry after doing diploma in civil engineering . You may try for B.Tech in civil engineering is lateral entry is your plan.If you want to join B.Tech CSE in Jadavpur University then you may clear WBJEE.

https://engineering.careers360.com/articles/wbjee

All the best