I have a 26 inch bike(Specialized Rockhopper 2007) with decent wheels and fork. I want a more slacker head tube and better geometry than what i have now. I might be interested in one of Ragley Marley, Ragley Piglet Ragley Bluepig frames. My fork is not tapered. I know there are some conversion rings for that. I wanted to know if i can transfer all parts from the present bike to this new frame. I am little bit apprehensive about quick releases. I heard some frames take thicker quick release rods.
Overall its probably cheaper and certainly easier to sell the bike you have and buy the one you want. Building a bike from a 27.5 frame with 26 components you may end up with a bike geometry that is 'out' and handles worse than you already have.
The new frame is likely a though axle, and may have a wider (Boost) spacing, meaning the rear hub will need adapters or replacing. The bottom bracket and seat post are unlikely to be compatible. You may need a new chain as the chain stay length could be longer.
Answering the core question here, no, it for most intents and purposes won't work to run 26" wheels and conventional trail/XC tires, say 2.4 or less, in a 27.5+ frame. The outside diameter of the tires is way smaller, dropping the BB height beyond practicality and into the realm of regular issues with pedal strike etc. It's almost exactly as though you were putting 26" on a 29er. (Tire OD is basically the same between 29x2.3ish and 27.5x2.8.)