UK Tier 2 General Query

Hi All,

Here is my understanding of the following , please correct me if I am wrong.

(1) CoS- The certificate of Sponsorship has a validity of 3 months, within which we need to apply for the Visa.

(2) CoS - CoS carries a joining date and we can enter UK 15 days prior to the joining date.

(3) Tier 2 general Visa - The visa once issued will have the start and end date.

(4) Person after getting the VISA can travel any time . Is there any time limit saying , we need to travel within 3 months of issuing the visa ?

Your kind response will really help me and many on this forum .

Thank you
-Rane