而,means And. It is a compartion of an essay.For example 她去了美国,而我去了中国(she travled in America and I went to China)。
而且means And. For example, 她不仅去了美国,而且还去了中国(she not only travled in America but also went to China)。The big difference is when u need use 而且 in one sentence, u also need use 不仅. 不仅。。。而且。。。not only...but also...
则,means Then . For example 如果她没有去美国,则她一定是去了中国。If she didnt go to America then she must go to China.
然而,却 the difference between 然而 and 却 like However and But .
他大可不必这么做,然而,他还是这么做了。(he couldn't have done it,but he did )
他大可不必这么做,他却这么做了。(he couldn't have done it,but he did)
Please correct my mistakes ,thanks a lot,and I hope it can help u learn chinese better