The solutions for Levels 21-25, including letter collection are as follows:
21 = ULDRR RDRUU RUDRL LDLUU LDURR UU
22 = URURD LLDLU ULDRD RURRR URUU
23 = ULDRL URULU LDLUR RRRUR DDLDR RRURU LDDDR ULDUU
24 = ULLDD RURLU DRUU
25 = URDLU RLLLU LURDU LDLUU