U can solve radial eqn using the following method, Near r=0 the differential equation for radial part is d^2u/dx^2=l(l+1)/r^2, now let u=r^s,then putting the value of u in the diiferential eqn, we gets(s-1)=l(l+1), therefore s=l+1, and the solution is u(r)=r^(l+1) or R(r)=r^l

Generally the angular and azimuthal parts are solved first and then radial but u can do either.

Thank you so much

In the book,the steps are not shown thats why,can you just show 2 or 3 steps,please?

Can you show the steps please?

Can you please say why is total derivative term the surface term?