**Sinuous Striker will die without dealing combat damage.**  Your opponent's creature will remain blocked, but will not be destroyed.

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The problem with this combo is that there is no way to activate Sinuous Striker's ability without state-based actions being checked immediately afterwards.  State-based actions are checked immediately after any ability resolves.

Let's assume that the Declare Attackers Step is complete.  Here is the order of events, all of which happen during the [Declare Blockers Step][1]:

 1. You declare that your Sinuous Striker will block your opponent's creature.<sup>509.1</sup>
 2. The active player (your opponent) gets priority.<sup>509.4</sup>
 3. Your opponent passes, giving you priority.<sup>116.3d</sup>
 4. You activate Sinuous Striker's ability twice.  You and your opponent both pass (twice) allowing both of those abilities to resolve.  Sinuous Striker is now a 4/0 creature.
 5. The active player (your opponent) will get priority after the spell resolves,<sup>116.3b</sup> so a check for state-based actions is triggered.<sup>704.3</sup>
 6. Sinuous Striker is destroyed by a state-based action.<sup>704.5f</sup>
 7. Combat damage is assigned.<sup>510.1</sup>  Your opponent's creature remains blocked<sup>510.1c</sup> but takes no combat damage.

  [1]: https://mtg.gamepedia.com/Declare_blockers_step