Is a Multiple Allele still belongs to Non-Mendelian patterns of inheritance?

Mendel did not study multiple allele type inheritance with his pea plant crosses. All the traits ( 7 different traits, I believe) that he studied were controlled be a single pair of genes (He called them "unit characters") , one being dominant and the other recessive. Answer to your question: Mult. alleles is non-Mendelian genetics.