All Sliver creatures have absorb 1. (If a source would deal damage to a Sliver, prevent 1 of that damage.)
If multiple sources would deal damage to a Sliver at once, prevent 1 damage from each of those sources.
If multiple replacement effects apply to a creature being dealt damage, the controller of the creature chooses the order to apply them, not the controller of the source of damage.
Abilities that Slivers grant, as well as power/toughness boosts, are cumulative. However, for some abilities, like flying, having more than one instance of the ability doesn't provide any additional benefit.
If the creature type of a Sliver changes so it's no longer a Sliver, it will no longer be affected by its own ability. Its ability will continue to affect other Sliver creatures.
