Entering Uk with 2 work visas

[a1s2s3]

Hi.

I have been in the UK for the past 2 years on a Tier 5 TW government exchange visa which is valid till September 2017 and I have the BRP for this. I am due to start a new job from August for which I have got Tier 2 sponsorship.

I have currently come to India to apply for the tier 2 general visa and have got my passport back today and the vignette states date valid from as 25/07/2017.

My query is that I have my graduation in the UK on the 20/07/2017 and had tickets booked for 18/07/2017. Can I still travel to UK on my current Tier 5 BRP which is valid till september? or can I enter only after 25/07/2017 as per new visa? And even if I do enter on 18/07 on tier 5 BRP, do I need to exit and re-enter for Tier 2 visa?

Thanks! Hoping for an urgent response as would need to reschedule tickets accordingly!

[iworker]

Once you get a new visa, the old visa is considered cancelled.
There is someone who recently entered using his old visa, but his old visa was visit, and he may have traveled from a visa free country.
In your instance, i think u cant enter.