Is it a hard problem to solve

We all know given P,aP,bP, to compute abP is a hard problem in elliptic
curve
my question is: Given abP,aP, to compute bP is a hard problem or not?

another question is like that:
there is a black-box, input xP, output xyP. The multiplication
parameter y is kept from any outsider. Is it possible for someone to
simulate the function of the black-box after some trainings?

The behavior can be depicted like that:
First, the attacker input a point sequence x_1P,x_2P,...,x_iP to the
black-box, and get corresponding output point x_1yP,x_2yP,...,x_iyP.
Then, after thoroughly analyzing the input-output pair, the attacker
tires to compute x_kyP without the help of black-box while x_k did not
occur in training phase.

regards!

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