Identification of Sunbirds
The bird in Picture-1 is  Purple-rumped sunbird (Leptocoma zeylonica) according to this decription from wikipedia:


  The males have a dark maroon upperside with a blue-green crown that glistens at some angles, bright green shoulder patch and violet/purple rump patch which is generally hidden under the wings. The underparts are whitish with dark throat, maroon breast band and purple/violet patch in the throat which is visible in some angles.




The birds in Pictures 2-5 is a single species, non-breeding male of purple sunbird (Cinnyris asiaticus) according to this description:


  The male is glossy metallic purplish black on the upper parts with the wings appearing dark brown. The breeding male has the underparts also of the same purplish black, but non-breeding males may show a central streak of black on yellow underparts.




References:


Wikipedia
r/whatsthisbird