Why in HL pair, H is stored after L register
The 8085 has seven internal 8-bit registers for data, called A, B, C, D, E, H, and L. Six of these registers can also be used in pairs to hold 16-bit quantities. These pairs are BC, DE and HL, where B, D and H hold the MSB of the value and C, E and L hold the LSB, respectively.

When these register pairs are transferred to/from memory, the LSB is always stored in the lower address and the MSB in the upper. The SHLD and LHLD instructions can be used to transfer the HL pair to/from an arbitrary address, while the PUSH and POP instructions can transfer any of the three pairs to/from the stack.

I hope this answers your question. I'm not sure what you mean when you say L is "used first".