I'm assuming you want to apply for Tier 2 from within the UK?

You can't directly switch to a Tier 2 unless you have a diploma or certificate of completion from your most recent grant of leave, which would be your second/current Tier 4. Unless this is the case, you are not exempt from the resident labour market test and need to apply for your Tier 2 visa from your home country.

• you have completed at least 12 months of study in the UK towards a UK PhD, or you have completed and passed a UK recognised Bachelor's or Master's degree or a UK Postgraduate Certificate in Education (PGCE) or Professional Graduate Diploma of Education (PGDE) – if you do not have your certificate, you can submit other evidence (academic transcript or reference) that must meet the requirements in the Tier 2 Policy Guidance

• you studied this course during your most recent period of immigration permission (leave) or during a period of continuous leave that includes this most most recent period of leave

Time spent on a Tier 4 visa doesn't count toward ILR (unless you're settling on Long Residence, i.e. 10 continuous years in the UK)