We consider two topics in scaling limits on Sierpi'nski carpet type fractals. First, we construct local, regular, irreducible, symmetric, self-similar Dirichlet forms on unconstrained Sierpi'nski carpets, which are natural extension of planar Sierpi'nski carpets by allowing the small cells to live off the $1/k$ grids. The intersection of two cells can be a line segment of irrational length, so the class contains some irrationally ramified self-similar sets. In addition, in this strongly recurrent setting, we can drop the non-diagonal condition, which was always assumed in previous works. We also give an example showing that a good Dirichlet form may not exist if we weaken more geometric conditions. Second, on any planar Sierpi'nski carpet, we prove the existence of the scaling limit of loop-erased random walks on Sierpi'nski carpet graphs. In addition, we have a more general result showing that the loop-erased Markov chains induced by the resistance form on a sequence of finite sets approximating the resistance space converge weakly in the Hausdorff metric. To prove this, we introduce partial loop-erasing operators, and prove a surprising result that, by applying a refinement sequence of partial loop-erasing operators to a finite Markov chain, we will get a process equivalent to the loop-erased Markov chain. All the limit probabilities are shown to be supported on the set of simple paths.