1.中国始终坚持与邻为善、以邻为伴的周边外交方针，重视与相邻国家建立边境地区信任措施，加强边境地区军队友好交往，积极预防危险军事活动，维护边境地区和平与稳定。
China consistently pursues an foreign policy of building an amical friendship and partership with its neighbors, attaches great importance to border area confidence-building measures, strenghtens friendly military exchanges in border areas, and actively  prevent dangerous military activities, all of which have helped preserve peace and stability on the borders.

词汇：
坚持……方针pursue a foreign policy of
与邻为善、以邻为伴an amicable relationship and partnership with its neighbors
重视attache great importance to sth.

译文采用动词并列，顺序没有太大变化，注意最后部分的翻译。
前面的一些措施，最终帮助实现“维护边境地区和平与稳定”，译文让句子内部关系更清晰。

2.在中央政府的大力扶持和全国各地支援下，西藏经济实现了历史性跨越。据统计，1959－2010年，西藏全社会固定资产投资累计完成2751亿元，年均增幅达到15％以上，其中1994－2010年，全社会固定资产投资累计2643亿元，年均增幅达到20％以上。

Thanks to the care of the Central Authorities and the suppor of the whold nation, Tibet has witnessed a historic leap in its economic and social development. From 1959 to 2010, fixed assests invesetment in the reign totaled 275.1 billion yuan, registering an average annual growth of over 15 percent. The figure was 264.3 billion yuan from 1994 to 2010, the annual growth rate in that period was more than 20 percent.

实现了历史性跨越witness a historic leap
固定资产投资fixed assets investment

断句：据统计，1959－2010年，西藏全社会固定资产投资累计完成2751亿元，年均增幅达到15％以上，||其中1994－2010年，全社会固定资产投资累计2643亿元，年均增幅达到20％以上。